In electronics modules comprising a plurality of electronics cards, it is common practice to use spacers for assembling the electronics cards together. Such spacers are either made of plastics material, or else they are made of metal material, with metal spacers also serving to provide electrical continuity between the electrical grounds of electronics cards.
Certain spacers, also known as “standoffs”, comprise an elongate body having one end that is tapped, defining a tapped hole, and a threaded segment extending from the other end of the elongate body.
FIG. 1 is a section view of a first electronics card 1 and a second electronics card 2 of an electronics module 3, the cards being assembled together by means of at least prior art spacer or standoff 4.
The body 5 of the spacer 4 is positioned between the cards 1 and 2 so that firstly the threaded segment 6 projects from the first card 1 through an optional washer 7 and an opening 8 formed in the first card 1, and secondly the tapped hole 9 is placed facing an opening 10 formed in the second card 2. A nut 11 is screwed onto the threaded segment 6, and a bolt 12 is screwed into the tapped hole 9 of the spacer 4 through the opening 10.
That assembly requires a large number of components to be used (a bolt, a nut, and a washer for each spacer), thereby increasing the cost of the electronics module and making it more complex to manage its bill of materials, obsolescence, supplies, etc.
To eliminate the nut and the washer, it might be envisaged that the spacer could be assembled by being fastened to the first card during a wave soldering operation consisting in applying solder directly to the thread of the spacer and over a reception area on the first card. A first drawback of fastening in that way is poor mechanical strength, due to the poor grip of solder on the thread, thereby limiting the tightening torque that can be applied to the bolt that penetrates into the tapping. A second drawback of such fastening is poor reproducibility in terms of the mechanical strength of the fastening, which means that is not possible to define a single tightening torque for all of the spacers, thereby making automatic assembly difficult to implement.